Cable Shielding Effectiveness Measurement

This method is effective for frequencies less than 500 megahertz.

Cable shielding effectiveness measurement.

Our most common request is to measure se for connectors and cables. A plot of the chamber s dynamic range is shown in figure 2. For these products we primarily use two techniques the triaxial fixture method and the mode stirred method. Measurement method for determining shielding effectiveness of cable feedthroughs.

For example housings connectors or cables all use shields and each application requires a unique test fixture to ensure accurate and repeatable se measurements. There could also be changes in compliance standards. When a cable specification calls for 90 db of rf shielding the 100 db dynamic range allows a 10 db margin in the measurement range. A shielding unit is inserted through the box s opening.

Making accurate measurements is a challenge because shields have many different shapes and purposes. An efficient and repeatable measurement method for determining shielding effectiveness of cable feedthroughs based on the use of nested reverberation chambers is presented. Measurements were made in the frequency range 0 5 to 100 mhz. The method is offered as a standard technique for measuring the shielding effectiveness of shielded cables.

The measurement method is validated by comparing measurements on an isolated conductor penetrating the shield with a simple theory based on basic circuit theory in combination with antenna theory. The shielding effectiveness is measured by comparing the reading of reference and the load devices. The test method permits measurement of long specimens using high currents with a uniform current distribution along the cable shield. To verify the periodic calibration two gold standards are employed.

Cable interconnects which allow cables inside the cage to connect to cables outside may undergo modification for additional connectors that damage the shielding integrity.